This invention relates to electrodes for cold-cathode discharge lamps.
Conventional gas discharge lamps take one of two forms. They are either of the hot-cathode or cold-cathode kind. In the hot-cathode kind, the electrodes are heated so that electrons are emitted from the cathode by primary emission; in the cold-cathode kind, ion bombardment of the cathode causes the secondary emission of electrons. Although hot-cathode lamps have a greater electrical efficiency, cold-cathode lamps have the advantage of a considerably longer life and maintain a more constant brightness over their life than hot-cathode lamps.
The electrodes of cold-cathode lamps are generally hollow, that is, they take the shape of a short tube having an open end and a closed end, the open end facing the opposite electrode. Electrodes of this shape have been found to produce a more stable discharge and require lower operating voltages than flat plate electrodes.
In GB 2244855 it is proposed to form the electrodes of a flat panel cold-cathode discharge lamp from blocks of conductive material extending along opposite sides of the lamp. The electrodes are machined with slots which extend across the width of the electrode between the two glass plates to form regions of high current density. It has been found that, with prolonged use, metal can be sputtered out of the slots onto the glass plates, leading to discoloration.